Fuel injection pumps for i.c. engines

ABSTRACT

A fuel injection pump for an internal combustion engine includes a pair of reciprocable pumping plungers which are moved inwardly to effect a pumping stroke by means of rollers carried by shoes engaging the plungers, the rollers engaging cam lobes. A stop is provided which has end portions lying in the path of movement of the shoes and the surfaces of the shoes and end portions of the leaf stop are so shaped that when lateral movement is imparted to the shoes, the extent by which the shoes can move outwardly, will be varied.

Unite States Patent 1 1 Bonin 1 Nov. 12, 1974 1 1 FUEL INJECTION PUMPS FOR LC.

ENGINES [75] Inventor: Jean-Claude Bonin, Blois, France 731 Assignee: Rdt61iseLC1ichyFauE dSein),

France [22] Filed: Dec. 19, 1972 [211 App]. No.: 316,485

[30] Foreign Application Priority Data Dec. 22, 1971 France 71.46180 [52] US. Cl 417/214, 417/462 [51] Int. Cl. F04b 49/00 [58] Field of Search 417/214, 462

[56] References Cited UNITED STATES PATENTS 2.828.697 4/1958 Roosa 417/462 3,000,318

9/1961. I Volossevich 417/214 3,046,905 7/1962 Davis 417/462 3.338,]68 8/1967 3.650159 3/1972 Garnier 1. 417/462 Primary Examiner-William L. Freeh Attorney, Agent, or FirmFinnegan, Henderson, Farabow & Garrett 57 ABSTRACT A fuel injection pump for an internal combustion engine includes a pair of reciprocable pumping plungers which are moved inwardly to effect a pumping stroke by means of rollers carried by shoes engaging the plungers, the rollers engaging cam lobes. A stop is provided which has end portions lying in the path of movement of the shoes and the surfaces of the shoes and end portions of the leaf stop are so shaped that when lateral movement is imparted to the shoes, the extent by which the shoes can'move outwardly, will be varied.

27 Claims, 9 Drawing Figures PAIENTEUHUV 12 IBM SHEET 2 OF 3 F'IGCv. FIG-4.

FIGS.

FIGS.

I NIEnunvmsm 3847509 SHEEI 30F 3 43 a FIG] FUEL INJECTION PUMPS FOR I.C. ENGINES This invention relates to fuel injection pumps for internal combustion engines and of the kind comprising a body part, a distributor member rotatable within the body part and adapted to be driven in timed relationship with an engine with which the pump is associated, a transverse bore formed in the distributor member, a pair of pumping plungers reciprocably mounted within the bore, a pair of roller shoes slidable in radial slots at the outer ends of said bore, the shoes engaging the plungers during inward movement of the shoes, cam engaging means carried by said shoes, an annular cam ring surrounding said distributor, cam lobes formed on the internal periphery of said cam ring and engaging with said cam engaging means during the rotation of said distributor member to impart inward movement to said shoes and plungers, fuel delivery means for conveying fuel disposed from said bore to a plurality of fuel outlets in turn, fuel inlet means for supplying fuel to said bore during the periods when the plungers can move outwardly and a leaf stop carried by the distributor member, said leaf stop having end portions positioned in the path of said shoes to limit the outward movement of the shoes and plungers thereby limiting the maximum amount of fuel which can be supplied by the injection pump.

Such an injection pump is well known and one of the problems with such a pump is the provision of excess fuel for starting purposes bearing in mind that it is essential to ensure that under normal running conditions no more than a predetermined maximum quantity of fuel can be supplied to the engine, said predetermined quantity being less than the quantity required for the starting of the engine.

The object of the invention is to provide such a pump in a simple and convenient form and in which excess fuel for starting purposes can be readily obtained.

According to the invention in a pump of the kind specified the contacting surfaces of the shoes and the end portions of the leaf stop are shaped so that relative movement of the shoes and end portions of the leaf stop in an axial direction will effect a variation in the permitted outward movement of the plungers.

According to a further feature of the invention the contacting surfaces of the shoes and the end portions of the leaf stop define a recess, the shoes being movable relative to the ends of the leaf stop to permit additional outward movement of the shoes to take place thereby to permit an additional quantity of fuel to be supplied by the pump.

According to a further feature of the invention the end portions of the leaf stop define a pluralityof axially spaced teeth the contacting surfaces of the shoes being provided with recesses into which upon relative movement of the shoes and leaf stop, the teeth of the stop can enter, thereby to increase the permitted outward movementof the shoes. v

According to a further feature of the invention the shoes are movable axially relative to the distributor member.

Examples of liquid fuel injection pumps in accordance with the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a sectional side elevation through one example of a pump,

FIG. 2 is a section on the line 2-2 of FIG. 1

FIG. 3 is a sectional view of a part of the pump, shown in FIG. 1 with the parts in one position,

FIG. 4 is a view similar to FIG. 3 showing the parts in an alternative position,

FIG. 5 is a developed view of a cam lobe and,

FIGS. 6, 7, 8 and 9 show alternative arrangements of pump.

With reference to FIGS. 1 and 2 of the drawings there is provided a body part 10 in which is located a rotary cylindrical distributor member 11 which at one end is adapted to be driven in timed relationship with an engine with which the pump is associated. At the opposite end of the distributor, there is mounted the rotary part 12 of a vane type feed pump having an inlet 13 from a source of liquid fuel and an outlet 14 for fuel under pressure. The output pressure of the feed pump is controlled in a manner such that it varies in accordance with the speed at which the distributor member is driven, and this is effected by means of a relief valve not shown. I

Formed in the distributor member is a transversely extending bore 15 in which is located a pair of reciprocable pumping plungers 16. The plungers 16 at their outer ends, contact shoes 17 disposed for radial movement within radial slots formed in the distributor member and each shoe carries a roller 18. The rollers cooperate with an annular cam ring 19 located within the body part and having on its internal periphery, a plurality of cam lobes the contour of which is seen'in greater detail in FIG. 5.'The plungers 16 together with the rollers and cam lobes constitute a high pressure injection pump, and the space between the plungers 16 communicates with a longitudinally extending passage 20 formed in the distributor member. At one end the passage 20 communicates with a radially disposed delivery passage 21 and this is arranged to communicate in turn with a plurality of outlet ports 22 which are formed in the body part and which communicate respectively with the injection nozzles of the associated engine. The communication of the delivery passage 21 with an outlet 22 occurs during the time that the plungers are being moved inwardly.

At another position the longitudinal passage 20 communicates with fourradially extending. inlet passages 23 and these are arranged to communicate in turn as the distributor member rotates, with an inlet port 24 formed in the body part. The port 24 communicates with the outlet 14 of the feed pump, and an adjustable throttle 25 is provided to determine the quantity of fuel which will flow through the port 24 to the injection pump during the time that the port 24 is in communication with a passage 23. V

In operation, during inward movement of the plungers 16 fuel is displaced to an injection nozzle of the associated engine whereafter during continued rotation of the distributor member, the passage 21 moves out of register with a port 22, and one of the passages 23 moves into register with the inlet port 24. When this occurs fuel flows to the transverse bore 15 and the plungers are moved outwardly so that a fresh charge of fuel is available for delivery to the associated engine when the plungers 16 are next moved inwardly.

Such pumps are well known and in order to control the maximum quantity of fuel which can be supplied to the engine during normal running irrespective of the setting of the throttle, a stop is provided to limit the maximum outward movement of the plungers 16. As

shown in FIG. 2 a leaf stop 26 is provided and this is retained relative to the distributor member 11 so as to rotate therewith by means of an adjusting screw 27. The leaf stop is formed from resilient material and has end portions 28 which are bent so that they lie in the path of the shoes 17 respectively. The contour of the distrib utor member is such that by screwing the screw 27 inwardly the end portions will move outwardly to permit increased separation of the plungers. Turning now to FIGS. 3 and 4 it will be seen that the end portions 28 are recessed to provide a plurality of teeth and also the outer surfaces of the shoes 17 are recessed in a complementary manner. It will also be seen from FIGS. 3 and 4 that the shoes are movable relative to the leaf stop 26 in the axial direction. In FIG. 4 the shoes are positioned in the excess fuel position so that the teeth can enter into the recesses in the shoes. In FIG. 3 the shoes are positioned in the normal maximum fuel position so that the teeth cannot enter into the recesses. It will be seen therefore that when the parts are in the position shown in FIG. 4 increased outward movement of the shoes and plungers can occur and therefore more fuel can be supplied. As shown in FIG. 5 downward movement of the roller represents outward movement of the roller as seen in FIGS. 1 and 2. Position N represents normal maximum fuel quantity and position S represents excess fuel for starting purposes.

In FIGS. 1 and 4 the parts are shown in the excess fuel position and axial movement of the shoes 17 will return the shoes to the normal position. For effecting such movement the shoes are provided with actuating elements 29. These are of channel form and the side walls engage the ends of the rollers 18 and shoes. The base walls of the elements are provided with elongated apertures through which the plungers extend into contact with the shoes. Moreover, the elements are provided with integral actuating rods 30 which extend through and are in screw thread engagement with-an actuating disc 31. slidably mounted on the distributor member. The rods carry at their outer ends nuts 32 which bear against the disc 31. The disc is urged away from the plungers by compression springs 33 surrounding the rods the springs being interposed between the disc and an abutment plate 34 which is axially and angularly fixed to the distributor member.

A latch is provided to retain the disc 31 in the position shown and this comprises a pivotal member 35 carried within a groove in the distributor member. The member 35 has a shaped end for engagement with the end of a sleeve forming part of the disc and it is loaded by a resilient band into the latched position shown. For releasing the latch there is provided in the particular example, a fluid pressure operable piston 36 which is located within a cylinder formed in the distributor member. The cylinder communicates with the outlet 14 of the feed pump and the arrangement is such that when the output pressure of the feed pump increases as when the engine has started the piston moves the latch to release the disc 31 which moves under the action of the springs at the same time effecting axial movement of the shoes to the position shown in FIG. 3. This movement may not occur immediately after the latch is released but will occur as soon as possible .when the pumping pressure is removed from the rollers. To facilitate this movement it will be noted from FIGS. 3 and 4, that the side faces of the teeth and recesses as are inclined.

Movement of the disc into the excess fuel position is effected by a movable member 37 shown in dotted outline in FIG. 1. When the member is moved towards the plungers it will contact the disc 31 which will also be moved axially and will be retained in this position by the latch 35.

In the arrangement shown in FIG. 6 a sleeve 38 surrounds the distributor member and is axially movable to obtain the normal and excess fuel positions. A catch comprising two oppositely movable relatively spring loaded catch members 39 is mounted in the distributor member and engage within detents in the sleeve 38. As shown the parts are in a position such that the normal fuel quantity is supplied. For movement of the parts into the excess fuel position a member 40 is provided which is engageable with a flange on the sleeve. Such movement of the member overcomes the force exerted by the catch members to that the sleeve moves to its alternative position. Means '41 is provided to return the sleeve to its original position when the engine has started. The means 41 may comprise a centrifugally operable device responsive to the speed of rotation of the engine of distributor member. This device may be the normal centrifugal governor fitted to the pump to control the setting of the throttle member 25. In any event the member 40, or its control linkage is arranged so that excess fuel can only be obtained when the engine is at rest.

In the arrangement shown in FIG. 7 the sleeve 42 is spring loaded by means of a spring 43 to a position in which excess fuel is supplied. The sleeve is movable in the opposite direction by the force exerted by pistons 44 housed within cylinders in the body. The pistons act on a thrust ring 45 which engages the actuating elements carrying the rollers and shoes. As will be seen from FIG. 7 an additional spring 46 is provided together with an abutment ring 47 for contact by the sleeve. When the sleeve contacts the abutment ring an additional load is imposed upon the movement of the sleeve and this in conjunction with additional stops which are not shown and which are suitably contoured, shape the maximum fuel delivery curve in a manner dependent upon the engine speed.

In the arrangement shown in FIGS. 8 and 9 the distributor member 11 is provided with a helically splined portion carrying helical splines 48 and which are engaged by complimentary splines formed on the internal periphery of a ring 49 engaged about the distributor member. Engaging with the end face of this ring are a pair of diametrically opposed actuating elements 50 which are formed integrally with and ring 51 slidably mounted upon a plain portion of the distributor member. The actuating elements are obliquely disposed and are located in complimentary grooves 52 formed in an enlarged portion of the distributor member. Conveniently the elements are disposed at the same angle as the helix angle of the splines.

The actuating elements are provided with slots 53 in which are located the shoes which support the rollers and furthermore the base walls of the slots are apertured to allow the plungers 16 to pass therethrough into contact with the shoes. The actuating elements are loaded in one direction in which excess fuel will be provided, by means of a spring 54 and are urged in the opposite direction by fluid pressure operable pistons as in the case of the example of FIG. 7. A leaf stop 55 is provided as in the previous examples and it is provided with teeth not shown, the shoes similarly being provided with recesses. When the actuating elements are moved by the pistons the outward movement of the rollers is limited as described, however, in addition by the action of the oblique grooves the rollers will move angularly about the axis of rotation of the distributor member and thereby the timing of injection of fuel will be adjusted.

I claim:

1. In a fuel injection pump for an internal combustion engine having a pair of reciprocable pumping plungers which are moved inwardly to affect a pumping stroke by means of rollers carried by shoes engaging the plungers, the rollers cooperating with cam means, and a leaf stop having end portions in the path of movement of the shoes, the improvement wherein the contacting surfaces of said shoes and the end portions of said leaf stop are shaped so that relative movement of said shoes and end portions of said leaf stop in an axial direction will effect a variation in the permitted outward movement of said plungers.

2. In a fuel injection pump for an internal combustion engine having a pair of reciprocable pumping plungers which are moved inwardly to affect a pumping stroke by means of rollers carried by shoes which engage said plungers, rollers engaging cam means, a leaf stop with end portions lying in the path of movement of said shoes, fuel delivery means for conveying fuel displaced by said plungers during inward movement thereof and fuel inlet means for supplying fuel to the space between said plungers during outward movement thereof the improvement comprising a recess defined in the contacting surfaces of said shoes to cooperatively engage the end portions of said stop, said shoes being movable relative to the ends of said stop to permit additional outward movement of said shoes to take place, thereby permitting an additional quantity of fuel to be supplied by said pump.

3. In the fuel injection pump as in claim 2 wherein the improvement further comprises said stop having end portions which define a plurality of axially spaced teeth, the contacting surfaces of said shoes being provided with recesses into which upon relative movement of said'shoes and said leaf stop, said teeth of said stop can enter, thereby increasing the permitted outward movement of said shoes.

4. In the fuel injection pump in claim 3 wherein the improvement further comprises a distributor member having said leaf stop mounted thereon, and in which said shoes are movable axially relative to said distributor member.

5. A pump as claimed in claim 4 including actuating members engageable with the shoes respectively, said actuating members being coupled to a member slidable axially upon the distributor member but rotatable therewith. i

6. In a fuel injection pump for an internal combustion engine having a pair of reciprocable pumping plungers movable inwardly to affect a'pumping stroke by means of rollers carried by shoes to engage said plungers, said rollers cooperating with cam means, and having a stop which has end portions in the path of movement of said shoes limiting the outward movement of said plungers, the improvement comprising actuating members of channel form, the internal side walls of said channel form actuating members engaging the ends of said respective shoes, the interior base wall of said channel form actuating members having an aperture formed therein through which said respective plunger projects to cooperate directly with said respective shoe.

7. The improvement of the fuel pump as claimed in claim 6 in which said actuating members are resiliently loaded towards the excess fuel position.

8. The improvement of the fuel pump as claimed in claim 7 including fluid pressure operable means for moving the actuating members towards the normal maximum fuel position.

9. The improvement of the fuel pump as claimed in claim 6 in which said actuating members are disposed obliquely in complementary slots in the distributor member, whereby as the actuating members move axially the rollers will also move angularly about the axis of rotation of the distributor member.

10. The improvement of the fuel pump as claimed in claim 9 in which said actuating members are moved against the action of resilient means by a fluid pressure operable piston.

11. The improvement of the fuel pump as claimed in claim 10 including aring disposed intermediate the actuating members and the pistons.

12. The improvement of the fuel pump as claimed in claim 11 in which said ring is carried on helical splines formed on the distributor member.

13. The improvement of the fuel pump as claimed in claim 6 including catch means operable to retain the actuating members in the excess fuel position, wherein said catch means comprises a pair of outwardly spring loaded catch members located within a bore in the distributor member, said catch members engaging respectively in a pair of detents in a sleeve constituting the member to which the actuating elements are coupled.

14. The improvement of the fuel pump as claimed in claim 13 in which a further pair of detents are provided said further pair of detents acting to retain the actuating members in the normal maximum fuel position.

15. The improvement of the fuel pump as claimed in claim 14 including means operable to move the actuating members to the excess fuel position and further means operable to move the actuating members to the normal maximum fuel position.

16. The improvement of the fuel pump as claimed in claim 15 in which said further means comprises a centrifugally operable device responsive to the speed of rotation of the associated engine.

17. The improvement of the fuel pump as claimed in claim 16 in which said centrifugally operable means forms part of the governor of the pump.

18. The improvement of the fuel pump as claimed in claim 16 in which the teeth and recesses have inclined side walls to facilitate relative axial movement thereof.

19. The improvement of the fuel injection pump as claimed in claim 6 further including fuel delivery means for conveying fuel from the space defined between said respective plungers during inward movement thereof, fuel inlet means for supplying fuel to the space defined between said plungers during outward movement thereof, catch means cooperatively connected with said actuating members to retain said members in a first fuel delivery position, and spring means cooperatively acting with said actuating members to allow further outward movement of said plungers to a second increased fuel delivery position once said catch means is released.

20. The improvement of the fuel pump as claimed in claim 19 in which said catch means comprises a pivotal member having one end shaped to engage and retain the member to which the actuating members are coupled, resilient means acting to retain the pivotal member in this position and fluid pressure operable means for moving said pivotal member out of engagement with said member thereby to allow the actuating members to move the shoes to the normal maximum fuel position.

21. The improvement of the fuel pump as claimed in claim 20 including means for moving the actuating members to the excess fuel position.

22. The improvement of the fuel pump as claimed in claim 21 in which the spring means biasing the actuating members encircles rods respectively coupling the actuating members to the aforesaid member.

23. The improvement of the fuel pump as claimed in claim 22 in which the teeth and recesses have inclined side walls to facilitate relative axial movement thereof.

24. The improvement of the fuel pump as claimed in claim 22 in which said resilient means comprises a coiled compression spring acting upon the member coupled to the actuating members.

25. The improvement of the fuel pump as claimed in claim 24 including a further coiled compression spring which acts upon said member after a predetermined movement thereof against the action of said coiled compression spring, the pump including additional contoured stop members for the shoes, and the fluid pressure for actuating said fluid pressure operable means being derived from a source whose output pressure varies in accordance with the speed at which the engine is driven.

26. The improvement of the fuel pump as claimed in claim 25 in which said source comprises a feed pump which supplies fuel to the injection pump said feed pump being provided with .a pressure control valve.

27. The improvement of the fuel pump as claimed in claim 26 in which said fluid pressure operable means comprises a plurality of pistons. 

1. In a fuel injection pump for an internal combustion engine having a pair of reciprocable pumping plungers which are moved inwardly to affect a pumping stroke by means of rollers carried by shoes engaging the plungers, the rollers cooperating with cam means, and a leaf stop having end portions in the path of movement of the shoes, the improvement wherein the contacting surfaces of said shoes and the end portions of said leaf stop are shaped so that relative movement of said shoes and end portions of said leaf stop in an axial direction will effect a variation in the permitted outward movement of said plungers.
 2. In a fuel injection pump for an internal combustion engine having a pair of reciprocable pumping plungers which are moveD inwardly to affect a pumping stroke by means of rollers carried by shoes which engage said plungers, rollers engaging cam means, a leaf stop with end portions lying in the path of movement of said shoes, fuel delivery means for conveying fuel displaced by said plungers during inward movement thereof and fuel inlet means for supplying fuel to the space between said plungers during outward movement thereof the improvement comprising a recess defined in the contacting surfaces of said shoes to cooperatively engage the end portions of said stop, said shoes being movable relative to the ends of said stop to permit additional outward movement of said shoes to take place, thereby permitting an additional quantity of fuel to be supplied by said pump.
 3. In the fuel injection pump as in claim 2 wherein the improvement further comprises said stop having end portions which define a plurality of axially spaced teeth, the contacting surfaces of said shoes being provided with recesses into which upon relative movement of said shoes and said leaf stop, said teeth of said stop can enter, thereby increasing the permitted outward movement of said shoes.
 4. In the fuel injection pump in claim 3 wherein the improvement further comprises a distributor member having said leaf stop mounted thereon, and in which said shoes are movable axially relative to said distributor member.
 5. A pump as claimed in claim 4 including actuating members engageable with the shoes respectively, said actuating members being coupled to a member slidable axially upon the distributor member but rotatable therewith.
 6. In a fuel injection pump for an internal combustion engine having a pair of reciprocable pumping plungers movable inwardly to affect a pumping stroke by means of rollers carried by shoes to engage said plungers, said rollers cooperating with cam means, and having a stop which has end portions in the path of movement of said shoes limiting the outward movement of said plungers, the improvement comprising actuating members of channel form, the internal side walls of said channel form actuating members engaging the ends of said respective shoes, the interior base wall of said channel form actuating members having an aperture formed therein through which said respective plunger projects to cooperate directly with said respective shoe.
 7. The improvement of the fuel pump as claimed in claim 6 in which said actuating members are resiliently loaded towards the excess fuel position.
 8. The improvement of the fuel pump as claimed in claim 7 including fluid pressure operable means for moving the actuating members towards the normal maximum fuel position.
 9. The improvement of the fuel pump as claimed in claim 6 in which said actuating members are disposed obliquely in complementary slots in the distributor member, whereby as the actuating members move axially the rollers will also move angularly about the axis of rotation of the distributor member.
 10. The improvement of the fuel pump as claimed in claim 9 in which said actuating members are moved against the action of resilient means by a fluid pressure operable piston.
 11. The improvement of the fuel pump as claimed in claim 10 including aring disposed intermediate the actuating members and the pistons.
 12. The improvement of the fuel pump as claimed in claim 11 in which said ring is carried on helical splines formed on the distributor member.
 13. The improvement of the fuel pump as claimed in claim 6 including catch means operable to retain the actuating members in the excess fuel position, wherein said catch means comprises a pair of outwardly spring loaded catch members located within a bore in the distributor member, said catch members engaging respectively in a pair of detents in a sleeve constituting the member to which the actuating elements are coupled.
 14. The improvement of the fuel pump as claimed in claim 13 in which a further pair of detents are provided said further pair of detents acting to retain the acTuating members in the normal maximum fuel position.
 15. The improvement of the fuel pump as claimed in claim 14 including means operable to move the actuating members to the excess fuel position and further means operable to move the actuating members to the normal maximum fuel position.
 16. The improvement of the fuel pump as claimed in claim 15 in which said further means comprises a centrifugally operable device responsive to the speed of rotation of the associated engine.
 17. The improvement of the fuel pump as claimed in claim 16 in which said centrifugally operable means forms part of the governor of the pump.
 18. The improvement of the fuel pump as claimed in claim 16 in which the teeth and recesses have inclined side walls to facilitate relative axial movement thereof.
 19. The improvement of the fuel injection pump as claimed in claim 6 further including fuel delivery means for conveying fuel from the space defined between said respective plungers during inward movement thereof, fuel inlet means for supplying fuel to the space defined between said plungers during outward movement thereof, catch means cooperatively connected with said actuating members to retain said members in a first fuel delivery position, and spring means cooperatively acting with said actuating members to allow further outward movement of said plungers to a second increased fuel delivery position once said catch means is released.
 20. The improvement of the fuel pump as claimed in claim 19 in which said catch means comprises a pivotal member having one end shaped to engage and retain the member to which the actuating members are coupled, resilient means acting to retain the pivotal member in this position and fluid pressure operable means for moving said pivotal member out of engagement with said member thereby to allow the actuating members to move the shoes to the normal maximum fuel position.
 21. The improvement of the fuel pump as claimed in claim 20 including means for moving the actuating members to the excess fuel position.
 22. The improvement of the fuel pump as claimed in claim 21 in which the spring means biasing the actuating members encircles rods respectively coupling the actuating members to the aforesaid member.
 23. The improvement of the fuel pump as claimed in claim 22 in which the teeth and recesses have inclined side walls to facilitate relative axial movement thereof.
 24. The improvement of the fuel pump as claimed in claim 22 in which said resilient means comprises a coiled compression spring acting upon the member coupled to the actuating members.
 25. The improvement of the fuel pump as claimed in claim 24 including a further coiled compression spring which acts upon said member after a predetermined movement thereof against the action of said coiled compression spring, the pump including additional contoured stop members for the shoes, and the fluid pressure for actuating said fluid pressure operable means being derived from a source whose output pressure varies in accordance with the speed at which the engine is driven.
 26. The improvement of the fuel pump as claimed in claim 25 in which said source comprises a feed pump which supplies fuel to the injection pump said feed pump being provided with a pressure control valve.
 27. The improvement of the fuel pump as claimed in claim 26 in which said fluid pressure operable means comprises a plurality of pistons. 